Sputum and plasma doxycycline concentrations after a single oral 600 mg doxycycline dose in patients with chronic bronchitis.

Plasma and sputum concentrations of doxycycline were measured in 10 patients with chronic bronchitis for a period of 96 h after a single oral 600 mg dose of doxycycline. The plasma doxycycline levels exceeded the minimal inhibitory concentrations (MIC) against common respiratory pathogens. Sputum doxycycline levels were detected in nine patients and these compared favourably with the above MICs for 24 h. The mean percent ratio of sputum/plasma doxycycline level reached a maximum of 28% at 48 h. There was a positive correlation between sputum and plasma doxycycline levels. This study provides pharmacokinetic support for a single oral 600 mg dose of doxycycline in the treatment of acute bronchial infection.